This is a blog I did some time ago, coaching people in what to look for and what questions to ask to help separate the good inspectors from the bad (there are good and bad in every profession). http://activerain.com/blogsview/206184/How-To-Hire-a
It's like anyone you hire - interview them well and hire the one who most impresses you.
Being a Realtor in the city of Philadelphia, my clients have used a variety of Home Inspectors. They have taken my recommendation and have tried on their own to find on, or had a friend in the business that they have used. You want to make sure the Inspection Company is well-known for their good work ethnic. Here in N.E. Philly, I usually recommend U.S. Inspect and Pilar to Post. You can also search the web or the yellow pages. A good website is http://www.ashi.org
Hope that helps.
"Third Generation Realtor"
Coldwell Banker Hearthside
a great way to find a home inspector is from your agent. Typically they will have three they usually recommend. I would also ask your friends and family in the area that have purchased a house recently as they will give you their honest opinion. Lastly try Angie's List if you cannot find anyone from the first two contact references. I recommend Apex home Inspections.